1. Field of the Invention
This invention is directed to drilling rigs with erectable masts and substructures; in certain particular aspects, to such rigs that are mobile; and methods for moving a drilling rig.
2. Description of Related Art
The prior art discloses a variety of rigs used in drilling and various wellbore operations, including rigs that are mobile; for example, and not by way of limitation, U.S. Pat. Nos. 3,340,938; 3,807,109; 3,922,825; 3,942,593; 4,269,395; 4,290,495; 4,368,602; 4,489,526; 4,569,168; 4,837,992; 6,634,436; 6,523,319 and the references cited in these patents—all these patents incorporated fully herein for all purposes.
In many land drilling operations, land rigs are delivered to a site, assembled and then disassembled; including, in many cases, raising a rig mast to a vertical operational position. Often as an oilfield becomes mature, wells are drilled deeper into the earth to obtain production. Oil rigs are getting progressively larger to meet these needs. In the past, a 1500 hp rig was sufficient to handle most drilling. These rigs more recently have been supplanted by larger 2000 hp rigs. Currently, 3000 hp rigs are being made, but are not yet widely used. A 3000 hp rig typically has a 36 to 37 foot high drillfloor, a 156 foot clear height mast, a 1,500,000 pound hookload, a 1,300,000 pound rotary load, and a 1,000,000 pound setback load. Often large drilling rigs, e.g. in the Middle East, are transported between well sites by dismantling the rig into pieces that can be trucked between two well sites which can produce many time-consuming truckloads of rig components resulting in up to four additional weeks of rig downtime (the larger the capacity of the rig, the heavier the loads, and the number of loads also increases); and mounting the drilling module complete with mast on tires. One drawback of a tire-mounted drilling module is tire load capacity and overall rig height. Often, the largest tires that are used are 40×57 earthmover tires.
With certain current rig designs, the largest rigs that can be easily moved are 2000 hp rigs of a box style substructure. This style of design is conducive to even tire loading. A typical 3000 hp rig that has an evenly loaded box style substructure will be too tall to move with a 156 foot mast and a 37 foot drillfloor to get under the power line height restriction with current moving systems (e.g. in countries such as Kuwait where a typical maximum clearance for power lines is 161 feet from the ground to the top of the rig being transported). Anything taller than this will produce the potential for electrical arcing between the mast and the power lines if the rig is being towed on its tires.
Another common style of substructure is the slingshot substructure which is often used in large hookload application. The substructure folds down in order to easily access the drillfloor from the ground level, which aids in rig assembly. Often a substructure of this size is broken down into truck sized loads. Placing a wheeled moving system on certain rigs of this style may not be practical because it is not feasible to easily balance the wheel loads.
U.S. Pat. No. 3,922,825 discloses a rig with a stationary substructure base and a movable substructure base mounted thereon which is coupled to the stationary base and swings upright into an elevated position on a series of struts that are connected to the stationary base with swivel connections at each end. The movable base is otherwise stationary since neither the stationary base nor the movable base are mobile or repositionable without the use of an auxiliary crane or the like. The movable substructure base and the drill mast are raised with a winch mounted on an auxiliary winch truck.
U.S. Pat. No. 3,942,593 discloses a mobile well drilling rig apparatus which has a trailerable telescoping mast and a separate sectionable substructure assembly with a rig base, a working floor, and a rail structure. The mast is conveyed to the top of the substructure by rollers and is raised by hydraulic raising apparatus to an upright position. With such a system the the mast assembly can be relatively long when transporting it and the mast can be unstable during raising. This system uses drawlines and winch apparatus to raise the mast onto the working floor.
U.S. Pat. No. 6,523,319 discloses a drilling rig base and a lower mast section that are collapsible into a compact transportable position. The base is expandable in the field to support a drilling platform and equipment, and the telescoping mast is also expandable for supporting the crown block and cables of the drawworks. The rig may have a plurality of beams, the outer beams being collapsible to a transportable position for placing on a single truck or trailer, and the A-frame lower mast section which is collapsible to a transportable position for placing on a single truck or trailer. In one aspect, a mobile, collapsible drilling rig base and drilling platform are disclosed which haves: a base having a plurality of parallel beams; the beams being in a horizontal plane and including inner beams and outer beams: the outer beams being collapsible in said horizontal plane to a transportable position; and a drilling platform attached to the base that is elevatable above the base.
U.S. Pat. No. 6,634,436 discloses a mobile land drilling apparatus and method. The rig has a mobile telescoping substructure box. A lifting apparatus selectively supports the mobile telescoping substructure box unit in a raised position and lowered position. An extension cylinder further extends the mobile telescoping substructure box unit in telescopic extension. A stationary frame member and a telescoping frame member have a plurality of cables attached thereto for supporting the telescoping frame member when extended. A trolley winch allows completion of the rig assembly without an external crane.
U.S. Pat. No. 7,357,616 discloses oil rig capable of being at least partially disassembled to form at least two portions, such as a top half and bottom half, and an associated structure for transport. An oil rig top portion may be loaded onto a trailer for transport separate from a bottom portion. The trailer includes a bottom frame, a top frame, a structure operably associated with said bottom and top frames for moving the top and bottom frames away from and towards one another, and a moving means attached to the at least bottom frame to allow the trailer to be moved along the support surface. The trailer may be towed by a truck or other vehicle. In one aspect a method is disclosed for transporting an oil rig, including: disassembling the oil rig to form a top portion with a rig floor and a mast and bottom portion with a substructure; transporting the top portion separately from the bottom portion; transporting the rig floor on a trailer; raising a top surface of the trailer to accept the rig floor; and prior to the step of transporting the rig floor on the trailer, lowering the top surface of the trailer. In one aspect, a trailer is disclosed for moving a part of an oil rig along a support surface, the trailer having: a bottom frame; a top frame; a structure operably associated with the bottom and top frames for moving the top and bottom frames away from and towards one another and further operative to temporarily fix the position of the top and bottom frames with respect to one another, the structure having at least one hydraulic piston; an alignment mechanism affixed to one of the top and bottom frame, the alignment mechanism operative to align the top frame with a top surface of the oil rig; an I-beam affixed to the top surface and operative to facilitate loading the part of the oil rig onto the trailer; and a moving means attached to at least the bottom frame to allow the trailer to be moved along the support surface.